The overall objectives of this study are to understand the factors leading to continued incidence of leprosy in the Philippines by novel molecular methodologies using a combination of retrospective and prospective sampling approaches. The overall objectives include: (1) strain typing of M. leprae isolates obtained from new and relapsed leprosy patients in the Philippines to identify clusters and transmission patterns when combined with conventional epidemiological criteria; (2) to determine the viability of M. leprae by mRNA detection in specimens collected from new patients; and those with signs of relapse; (3) to identify and determine the extent of mutations conferring resistance in past and circulating M. leprae isolates from leprosy patients to two Multidrug therapy (MDT) drugs; Dapsone and Rifampicin and; (4) to detect chains of transmission in endemic populations by a retrospective analyses of isolates in sample banks when combined with strain typing information from new cases and conventional epidemiological criteria. The following are the outcome measures for each of the objectives: (1) strain typing: identification of genotypes; (2) percent of samples from patients and their contacts containing viable M. leprae (as judged by the presence of mRNA for a panel of M. leprae genes; (3) percent of samples from patients and their contacts containing mutations in M. leprae rpoB and folP 1 genes and identification of new mutations associated with relapse and; (4) identification of matching or similar genotypes in new samples obtained from patients and their household contacts with those in retrospective samples. Clinical specimens that contain M. leprae bacilli such as skin biopsy, slit skin smears, nasal swabs and blood are required to obtain M. leprae DNA to meet the objectives of the study. Nasal swabs will be used for assessing the role of the nasal mucosa in infection and dissemination in leprosy. The blood is useful for monitoring the humoral responses to infection. Skin biopsy, slit skin smears, nasal swabs and blood will be obtained from informed consenting patients. Enrollment and sample collection procedures will take approximately 1-2 hours. These procedures will be performed during the patient's visit to the clinic for diagnosis and therapy for leprosy. As part of the study, a punch biopsy from a lesion is being collected to enable sufficient quantities of DNA to be extracted for strain typing, a critical objective of this study. Patients will be required to visit the site once more after 7-10 days to assess the biopsy site. This visit may take 30-60 minutes. An epidemiology survey containing demographic and clinical information will be obtained from each participant. Study participants for prospective sample collections will include volunteering and consenting individuals, 18 years old and above, reporting at Leonard Wood Memorial (LWM) CebuSkin Clinic, Leonard Wood Memorial Center for Biomedical Research, Cebu, Philippines for the diagnosis of leprosy and/or relapse of leprosy.